Stabilizing High-Valence Copper(I) Sites with Cu-Ni Interfaces Enhances Electroreduction of CO 2 to C 2+ Products.

In this study, the copper-nickel (Cu-Ni) bimetallic electrocatalysts for electrochemical CO ₂ reduction reaction(CO ₂ RR) are fabricated by taking the finely designed poly(ionic liquids) (PIL) containing abundant Salen and imidazolium chelating sites as the surficial layer, wherein Cu-Ni, PIL-Cu and PIL-Ni interaction can be readily regulated by different synthetic scheme. As a proof of concept, Cu@Salen-PIL@Ni(NO ₃ ) ₂ and Cu@Salen-PIL(Ni) hybrids differ significantly in the types and distribution of Ni species and Cu species at the surface, thereby delivering distinct Cu-Ni cooperation fashion for the CO ₂ RR. Remarkably, Cu@Salen-PIL@Ni(NO ₃ ) ₂ provides a C2+ faradaic efficiency (FE _C2+ ) of 80.9% with partial current density (j _{C 2+} ) of 262.9 mA cm ^-2 at -0.80 V (versus reversible hydrogen electrode, RHE) in 1 m KOH in a flow cell, while Cu@Salen-PIL(Ni) delivers the optimal FE _C2+ of 63.8% at j _C2+ of 146.7 mA cm ^-2 at -0.78 V. Mechanistic studies indicates that the presence of Cu-Ni interfaces in Cu@Salen-PIL@Ni(NO ₃ ) ₂ accounts for the preserve of high-valence Cu(I) species under CO ₂ RR conditions. It results in a high activity of both CO ₂ -to-CO conversion and C-C coupling while inhibition of the competitive HER.
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